Designing biochar through controlled synthesis: Correlating processing conditions with functional performance

Biochar is an increasingly studied material due to its remarkable structural versatility and multifunctionality, which make it suitable for applications ranging from environmental remediation to catalysis, agriculture, and advanced material synthesis. This review presents a comprehensive and structured analysis of the relationships between biochar synthesis parameters (e.g., feedstock type, pyrolysis conditions, activation strategy, and post-treatment) and the resulting physicochemical properties of the material, including porosity, surface area, functional groups, and surface charge. Particular attention is given to how these characteristics influence performance in key application fields, including pollutant adsorption, catalysis, bioenergy (e.g., hydrogen, and methane production), carbon-based nanomaterials, and soil improvement. The review highlights the complexity of the synthesis–structure–function relationships and emphasizes the importance of rational design approaches. By consolidating diverse experimental findings, this work aims to provide a conceptual and design-oriented framework for guiding the tailored design of biochar, offering qualitative predictive insights into how synthesis conditions and feedstock characteristics influence material properties and application-specific performance. • Intermediate pyrolysis enhances metal and hydrophilic organic adsorption. • Woody biomass boosts metal adsorption; sludges are best for lead removal. • Woody biomass at moderate temperature enhances anaerobic digestion. • Biochar can replace graphite in carbon nanomaterial synthesis. • Rational design links synthesis, structure, and application performance.